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MISSION OPERATIONS DIRECTORATE FLIGHT DIRECTOR OFFICE
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  1. MISSION OPERATIONS DIRECTORATE FLIGHT DIRECTOR OFFICE ENTRY OPTIONS TIGER TEAM DA8/LeRoy Cain April 22, 2003

  2. ENTRY OPTIONS Agenda/Contents • Previous Results - Summarized • STS-107 Weight Reduction Scenarios • Results - Summarized • Weight Reduction - Details/Assumptions • Weight Reduction Combinations - Scenarios 1,2, & 3 • Cold Soak Results - Summarized • Conclusions DA8/LeRoy E. Cain/x30705

  3. ENTRY OPTIONS Previous Results - Summary • Best case sensitivity study using certified deorbit targeting and STS-107 trajectory initial conditions to evaluate wing leading edge (WLE) and two body points, one forward and one aft of MLG door. (see Backup Chart 1 for diagram) • Control parameters: altitude, weight, c.g., crossrange, N-cycles (trajectory steepness), approach (ascending/descending), hemisphere (atmosphere), and prebank. • Results were as follows: • No significant thermal relief for any single control variable. • Best case control variable combinations: • WLE body point 5505 (RCC ): ~ 5% reduction in WLE max. temp. • Body point 1602 (tile): ~ 20% reduction for heat load, ~ 30% reduction for heat rate. • Body point 2360 (tile): ~ 20% reduction for heat load, ~ 40% reduction for heat rate. • Caveats to results: • All results were for a “no damage” scenario. For damage, the heat load and heat rate reductions would likely not be directly applicable, depending on the degree of damage. • Best case combinations were not proven to be achievable. • Analysis results verified our previous understanding: Using certified deorbit targeting methods, the only way to reduce the STS-107 heating profile would be to significantly reduce the weight (while maintaining acceptable c.g.) and to lower the orbit altitude prior to deorbit. DA8/LeRoy E. Cain/x30705

  4. ENTRY OPTIONS STS-107 Weight Reduction Scenarios • OVE WG (3/17/03) and PRCB (3/13/03) direction was to finalize the best case analyses for STS-107 initial conditions, and to not pursue development of any uncertified or contingency deorbit/entry profiles at this time. • The team developed three different weight reduction scenarios for STS-107, and combined them with other best-on-best case conditions (altitude reduction, approach trajectory, etc.) as in previous analyses. • Best case weight reduction categories included consumables (ECLSS, APU, Cryo, Prop), deployable items (middeck, flight deck, crew equipment, avionics, Spacehab), and jettison items (Spacehab, FREESTAR/GAS cans, and radiator panels). • Categories of weight reduction were not verified achievable, either alone (e.g. consumables), or in combination with other categories. • For each of the weight reduction scenarios, we assumed we could do it all. • This may not be realistic for some of the scenarios – the goal was to find the upper bound on the weight reduction. • Deployable and jettison items were grouped into scenarios that were limited only by available EVA time (12 hours). • The associated entry trajectories were simulated, the results of which were analyzed using the TSEP model. DA8/LeRoy E. Cain/x30705

  5. ENTRY OPTIONS Results - Summary • Weight reduction scenario 3 (consumables, deployable items, Spacehab jettison, and FREESTAR jettison) yielded the best results, with a total weight reduction of 31,321 lbm. • Using certified deorbit targeting and STS-107 trajectory initial conditions, and the best case combination of other control variables, scenario 3 yielded the following results: • WLE body point 5505 (RCC): ~ 7% reduction in WLE max. temp. • Body point 1602 (tile): ~ 24% reduction heat load, ~ 34% reduction heat rate. • Body point 2360 (tile): ~ 29% reduction heat load, ~ 56% reduction heat rate. • Caveats to results: • Detailed risk assessment was not performed, however it is clear that the increase in risk would be very significant in order to achieve these weight reductions. • Numerous flight rule violations (e.g. consumables management, EVA, etc.). • Numerous undocumented/unverified procedures (e.g. EVA jettison tasks, IFM, etc.). • Combination of weight reduction categories (consumables, deployable items, and jettison) was not verified to be feasible (timeline, crew workload, detailed EVA task, etc.) • All results were for a “no damage” scenario. For damage, the heat load and heat rate reductions would likely not be directly applicable, depending on the degree of damage. • Best case combination of trajectory variables was not proven to be achievable. DA8/LeRoy E. Cain/x30705

  6. ENTRY OPTIONS Results – Summary (Cont’d) • Weight reduction scenario 1 (consumables, deployable items, Spacehab deployable items, GAS cans, and radiator panels) yielded a total weight reduction of 20,387 lbm, the results of which were: • WLE body point 5505 (RCC): ~ 6% reduction in WLE max. temp. • Body point 1602 (tile): ~ 17% reduction heat load, ~ 33% reduction heat rate. • Body point 2360 (tile): ~ 23% reduction heat load, ~ 46% reduction heat rate. • Weight reduction scenario 2 (consumables, deployable items, Spacehab deployable items, radiator panels, and FREESTAR jettison) yielded a total weight reduction of 22,924 lbm, the results of which were: • WLE body point 5505 (RCC): ~ 6% reduction in WLE max. temp. • Body point 1602 (tile): ~ 18% reduction heat load, ~ 33% reduction heat rate. • Body point 2360 (tile): ~ 23% reduction heat load, ~ 45% reduction heat rate. • Caveats to results: • Same as for Scenario 3 • Trajectory/TSEP data included in backup charts. DA8/LeRoy E. Cain/x30705

  7. ENTRY OPTIONS Weight Reduction – Consumables • Consumables (total reduction 4159 lbm) • ECLSS (total 650 lbm) • All supply water tanks other than tank A dumped to zero (393). • Waste tank to minimum (79). • Both ammonia (NH3) tanks depleted (92). • GN2 systems at minimums (86). • APU/HYD (total 560 lbm) • One APU run to depletion (278). • Other two APU’s run to minimum quantities (222). • Cooling water (WSB) reduction due to APU run time (60). • Cryo H2/O2 (total 1600 lbm) • Tanks 3-9 (EDO and Orbiter) reduced to minimum residuals. • Remaining cryo vented overboard through relief valves. • Tank heaters used to over-pressurize tanks. • Excess cryo at the end of the mission could be “dumped” in less than one day. • Tanks 1 and 2 at minimums to support deorbit/entry. DA8/LeRoy E. Cain/x30705

  8. ENTRY OPTIONS Weight Reduction – Consumables (Cont’d) • Consumables (cont’d) • PROP (total 1349 lbm) • FRCS dumped to zero – nominal ops. • ARCS reduced to minimum to support mean entry to 0.05g, at which point exactly 20% remains (1349). • Impacts include numerous flight rule violations and undocumented procedures. • Absolute minimums in critical systems. • No deorbit waveoff opportunities. • No postlanding capability (cooling or power). • Zero fault tolerance, or reduced fault tolerance. • Itemized weight/c.g. details included in backup charts. DA8/LeRoy E. Cain/x30705

  9. ENTRY OPTIONS Weight Reduction – Deployable Items • Deployable items (total reduction 16,228 lbm) • All loose items, and items that could be made loose (via IFM, for example) and deployed overboard via EVA. • Items included from the following areas: • Middeck, flight deck, avionics bays (LRU’s), crew equipment (4663). • Spacehab module - systems, experiment payloads, racks (8017). • GAS cans (1891). • Radiator Panels (1657). • Itemized weight/c.g. details included in backup charts. DA8/LeRoy E. Cain/x30705

  10. ENTRY OPTIONS Weight Reduction – Spacehab Jettison • Perform EVA to disconnect Spacehab module and jettison from payload bay. (18,071 lbm) • Use EVA torque multiplier tool to open all four sill passive latches, and use EVA pins to restrain floating latches. • Disconnect 23 electrical and water lines running from Orbiter to Spacehab. • Use EVA cable cutters to physically disconnect lines. • Only one inhibit to remove power prior to cutting lines. • Disconnect Spacehab from tunnel adapter at the flexible joint. • Flexible joint material is Kevlar, cloth, and wiring. • May have been able to use EVA and IFM tools to cut through joint. • Two potential options for getting Spacehab out of payload bay: • EVA crew (two) pull Spacehab out of the closed keel latch and open sill latches to gain clearance for Orbiter backaway. • Perform slow Orbiter backaway while Spacehab is in open sill latches and closed keel latch. • Impacts and Unknowns • No experience base to determine feasibility of either option. • EVA crew pull SH out of the keel latch – unknown forces. No foot restraints available, so task would be free floating. • Dynamics of separation from closed keel latch has not been analyzed. DA8/LeRoy E. Cain/x30705

  11. ENTRY OPTIONS Weight Reduction – FREESTAR Jettison • Perform EVA to disconnect FREESTAR and jettison from payload bay. (4428 lbm) • Use EVA torque multiplier tool to open all four sill passive latches, and use EVA pins to restrain floating latches. • 8 electrical lines running from Orbiter to FREESTAR. • Use EVA cable cutters to physically disconnect lines. • Only one inhibit to remove power prior to cutting lines. • Impacts and Unknowns • Same options and concerns as Spacehab for getting FREESTAR out of payload bay. • Probably more feasible than SH jettison, from a mass handling perspective. • STS-107 only had two EVA latch pins manifested. • If both SH and FREESTAR were jettisoned, would need alternate means for restraining 2 floating passive latches. DA8/LeRoy E. Cain/x30705

  12. ENTRY OPTIONSFREESTAR/Spacehab Jettison and Separation • Assume that EVA crew will completely detach FREESTAR (or Spacehab) and provide a clear path up out of the payload bay. • Separation technique: • Orbiter performs small +Z body translation in free drift to slowly back away from FREESTAR (or Spacehab). • When FREESTAR (or Spacehab) clears the Orbiter mold line, the Orbiter will return to attitude hold and execute a standard separation sequence. • Separation Maneuver (1/2/3 Separation) Orbit Ops Checklist. • Provides a safe separation for any attitude. • Impacts and Unknowns • Small risk assuming the payload to be jettisoned is completely detached and cannot hang up as it exits the payload bay. • Separation techniques and procedures are published and well understood. DA8/LeRoy E. Cain/x30705

  13. ENTRY OPTIONSWeight Reduction Combinations – Scenarios 1 thru 3 • Table includes weight reduction categories used to develop combination scenarios. ItemDescriptionWeight Reduction A Consumables 4159 B Deployable Items (Middeck, 4663 Flight Deck, Avionics, Crew Equip.) C Deployable from Spacehab (1) 8017 D GAS Cans (2) 1891 E Radiator Panels 1657 F FREESTAR Jettison 4428 G Spacehab Jettison 18071 (1) – Item C is a subset of the total weight from item G. (2) – Item D is a subset of the total weight from item F. DA8/LeRoy E. Cain/x30705

  14. ENTRY OPTIONSWeight Reduction Combinations – Scenarios 1 thru 3 (Cont’d) • Three scenarios were developed from logical combinations of the items listed in the table. • Scenario 1: Total weight reduction = 20,387 lbm • Weight/c.g. changes resulting from combination of items A thru E. • Includes consumables, deployable items, SH deployable items, GAS cans, and radiator panels. • Assumes risks associated with jettison of Spacehab or FREESTAR are too great, or jettison unsuccessful (e.g. cannot physically detach). • Scenario 2: Total weight reduction = 22,924 lbm • Weight/c.g. changes resulting from combination of items A, B, C, E & F. • Includes consumables, deployable items, SH deployable items, radiator panels, and FREESTAR jettison. • Assumes risks associated with jettison of Spacehab are too great, or jettison unsuccessful (e.g. cannot physically detach). DA8/LeRoy E. Cain/x30705

  15. ENTRY OPTIONSWeight Reduction Combinations – Scenarios 1 thru 3 (Cont’d) • Scenario 3: Total weight reduction = 31,321 lbm • Weight/c.g. changes resulting from combination of items A, B, F &G. • Includes consumables, deployable items, FREESTAR jettison, and Spacehab jettison. • Radiator panel jettison was not included, because it was assumed that the EVA time required to perform both FREESTAR and SH jettison, as well as to deploy all other “deployables” would not leave time to also execute radiator jettison. • Assumes FREESTAR and Spacehab EVA jettison techniques can be developed and executed. • Itemized weight/c.g. details for all three scenarios included in backup charts. DA8/LeRoy E. Cain/x30705

  16. ENTRY OPTIONSWeight Reduction Combinations – Scenarios 1 thru 3 (Cont’d) • General Overriding Assumptions • Decision to perform weight reduction occurs early enough in the mission to develop the required plans and techniques. • Consumables – usage, overboard dumps, depletion burns, etc. • Deployable Items - required IFM’s, “deploy packaging”, etc. • Deployable Items - required EVA’s, Orbiter maneuvers. • Jettison Items - required EVA’s for detaching, jettisoning, cleanup of payload bay, etc. • Excessive risks associated with any of the three options (Scenario 1,2, or 3, or any other combination) would require that significant, and convincing data exists proving that the Orbiter could not survive entry. • Any and all possible weight reduction might be considered, depending on degree of concern, and time available. DA8/LeRoy E. Cain/x30705

  17. ENTRY OPTIONS Results - On-Orbit Coldsoak Post-Flight Analysis • The STS-107 EOM attitude timeline did provide cold wings for entry. • Actual EI temps were 6 degF and 3 degF on lower and upper surfaces, respectively (temp. limit is 92 deg at EI). • Best case left wing cold soak protecting all STS-107 thermal constraints (MLG tires, PLBD BET, structure, wave-off days), ECLSS, pointing and payloads yielded a 10 deg reduction in the left wing temp at EI. • Best case, protecting only a single deorbit opportunity, cold soaking for 2 days, yielded a 50 deg reduction in left wing temp at EI. • Best case, maximum possible cold soak (2+ days) and not protecting any other constraints yielded a 65 deg reduction in left wing temp at EI. • Reductions limited by low beta angle on STS-107. • These EI wing temperature reductions are not significant. • On STS-107, wing temps may have increased as much as 700 deg in 400 seconds (1.75 deg/sec) post EI. • A 65 deg decrease in EI wing temp would have resulted in ~37 second delay in onset of same max. temps and heat load. DA8/LeRoy E. Cain/x30705

  18. ENTRY OPTIONSConclusions • Using certified deorbit/entry targeting: • WLE: No appreciable temperature reduction, even when considering extreme Orbiter weight reductions (Scenario 3). • Body points (Tile): Some heat rate and heat load reduction is possible with moderate-to-extreme Orbiter weight reductions (Scenarios 1 thru 3). • For damage scenarios, the reductions would likely not be directly applicable, depending on the degree of damage. • In the final analysis, must balance heat rate and heat load for all body points. • Variations of the individual sensitivity parameters do not yield any significant results, especially for WLE. • Weight reduction scenarios to yield thermal relief are extremely aggressive and carry significant risk. • Have not identified method for determining if reduction in heat rate and heat load for bottom surface tiles is meaningful, especially for damage scenarios. DA8/LeRoy E. Cain/x30705

  19. ENTRY OPTIONS Forward Work Considerations • No further work is planned for STS-107 entry options. • No further work is planned for development of uncertified or contingency deorbit/entry profiles. • If requested (as part of Return-to-Flight efforts, or otherwise), primary candidates have been identified for consideration: • High angle of attack (WLE relief). • Low angle of attack (bottom surface relief). • High drag and low drag cases. • Process could yield pros/cons for WLE and other body points in each case - i.e. higher alpha reduces WLE heat rate, but increases heat load for other body points. • Currently no way to know whether or not these efforts would yield a viable contingency capability to optimize for TPS damaged areas. DA8/LeRoy E. Cain/x30705

  20. ENTRY OPTIONS Backup Charts • Orbiter Body Points Diagram • Trajectory/TSEP Data Plots • Consumables – Weight/CG Details • Deployable Items – Weight/CG Details • Weight Reduction Scenarios – Weight/CG Details • Sample Wing Leading Edge Stagnation Temperature • Sample Lower Surface Heat Rate • Sample Drag Profile DA8/LeRoy E. Cain/x30705

  21. ENTRY OPTIONSOrbiter Body Points TSEP model includes 29 body points used by USA Flight Design for commit to flight analysis. Utilized to evaluate key body points individually: Wing Leading Edge Stagnation Temperature (Body Point 5505 - RCC Panel 9) Wing Lower Surface Heat Rate (Body Point 2360 - aft of MLG door). Mid Fuselage (Body Point 1602 - forward of MLG door) DA8/LeRoy E. Cain/x30705

  22. ENTRY OPTIONSTrajectory/TSEP Data (see following charts) DA8/LeRoy E. Cain/x30705

  23. DA8/LeRoy E. Cain/x30705

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  25. DA8/LeRoy E. Cain/x30705

  26. DA8/LeRoy E. Cain/x30705

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  31. ENTRY OPTIONSConsumables - Weight/CG Details DA8/LeRoy E. Cain/x30705

  32. ENTRY OPTIONS Deployable Items - Weight/CG Details DA8/LeRoy E. Cain/x30705

  33. ENTRY OPTIONS Deployable Items - Weight/CG Details (cont.) DA8/LeRoy E. Cain/x30705

  34. ENTRY OPTIONS Deployable Items - Weight/CG Details (cont.) DA8/LeRoy E. Cain/x30705

  35. ENTRY OPTIONS Deployable Items - Weight/CG Details (cont.) DA8/LeRoy E. Cain/x30705

  36. ENTRY OPTIONS Weight Reduction Scenarios - Weight/CG Details Scenario 1: Total weight savings = 20,387 lbsWeight/cg changes from items A, B, C, D, and E WeightXcgYcgZcg Entry Interface 214088.6 1098.60 -0.18 370.38 TAEM 213611.1 1097.66 -0.17 370.20 Landing 213529.8 1099.37 -0.16 367.50 Scenario 2: Total weight savings = 22,924 lbs Weight/cg changes from items A, B, C, E, and F WeightXcgYcgZcg Entry Interface 211551.6 1098.35 -0.26 370.11 TAEM 211074.1 1097.39 -0.25 369.93 Landing 210992.8 1099.12 -0.24 367.19 DA8/LeRoy E. Cain/x30705

  37. ENTRY OPTIONS Weight Reduction Scenarios - Weight/CG Details Scenario 3: Total weight savings = 31,321 lbs Weight/cg changes from items A, B, F, and G WeightXcgYcgZcg Entry Interface 203154.9 1107.83 -0.68 369.52 TAEM 202677.4 1106.85 -0.67 369.33 Landing 202596.1 1108.66 -0.66 366.48 • For a baseline comparison, the following are the predicted end-of-mission mass properties from STS-107. WeightXcgYcgZcg Entry Interface 234477.0 1078.91 -0.56 371.97 TAEM 233999.5 1078.00 -0.55 371.81 Landing 233918.2 1079.56 -0.54 369.35 DA8/LeRoy E. Cain/x30705

  38. Peak Temperature: SODB Vol. V Limit* 2959 deg F STS-107 2909 deg F STS-90 2896 deg F STS-99 2939 deg F STS-105 2910 deg F STS-108 2913 deg F STS-109 2869 deg F STS-113 2858 deg F *Limit recently changed to 2999 deg F LMG Brake Line Temp D Start of off nominal trend LOS Entry Interface DA8/LeRoy E. Cain/x30705

  39. ENTRY OPTIONS Lower Surface Heat Rate – Multiple Flights DA8/LeRoy E. Cain/x30705

  40. ENTRY OPTIONS Sample Drag Profile DA8/LeRoy E. Cain/x30705